Field of the Invention
The present invention relates to a thin film type piezoelectric element substantially containing no lead therein, and a method of manufacturing the piezoelectric element. The present invention also relates to a piezoelectric actuator, a liquid ejection head, a liquid ejection apparatus, a vibration correction mechanism, a variable optical member, a movable optical member, an optical device, an image pickup apparatus, an optical switch, a micromirror device, an ultrasonic wave probe, an ultrasonograph, a sound component, an angular velocity sensor, a vibration power generator, a surface acoustic wave generator, a piezoelectric shutter, and an electronic apparatus using the piezoelectric element.
Description of the Related Art
A thin film type piezoelectric element typically includes a lower electrode, an upper electrode, and a piezoelectric film sandwiched therebetween. The piezoelectric film is formed of a polycrystal of a ferroelectric metal oxide. A typical principal component of the piezoelectric film is an ABO3 type perovskite-type metal oxide, e.g., lead zirconate titanate (hereinafter referred to as “PZT”). However, PZT contains lead as an A-site element, and thus, influence thereof on the environment is perceived as a problem. Therefore, a piezoelectric film containing no lead therein (lead-free piezoelectric film) is required.
As a lead-free piezoelectric film, a barium titanate film and a calcium barium zirconate titanate film as a partial substitution product thereof are known. In Japanese Patent Application Laid-Open No. 2004-006722, there is disclosed a (Ba, Ca, Sr) (Ti, Zr, Hf)O3 piezoelectric film that is oriented in a specific crystal orientation and is excellent in initial piezoelectric properties.
However, the oriented piezoelectric film is manufactured based on crystal lattice consistency between the piezoelectric film and a buffer layer thereunder, and thus, stress due to lattice misfit or difference in thermal expansion coefficient is produced in the film. Further, in the piezoelectric film, it is difficult to precisely control a composition ratio between an alkaline-earth metal at an A-site and a transition metal at a B-site, and thus, a number of site deficits (oxygen deficits and the like) exist in the film. Because of such internal stress and site deficits, when an oriented piezoelectric film as in Japanese Patent Application Laid-Open No. 2004-006722 is continuously driven, there are problems such as lowered piezoelectric properties (piezoelectric constant and the like), separation between the piezoelectric film and a substrate, and a crack developed in the piezoelectric film.
In order to deal with such problems, there is a technology of suppressing a crack by adding a manganese oxide of 2 mol % or more and 4 mol % or less to a nonepitaxial oriented barium zirconate titanate film as in, for example, Japanese Patent Application Laid-Open No. 2011-243722. The manganese component is expected to have the effect of compensating for site deficits in the piezoelectric film.
However, in a piezoelectric film having a composition as in Japanese Patent Application Laid-Open No. 2011-243722, there is another problem in that the added manganese component moves through the piezoelectric film while the piezoelectric element is manufactured or driven to react with a metal forming an electrode. As a result, the piezoelectric properties are lowered while the piezoelectric element is continuously driven.